1. Field of the Invention
The present invention relates to a laser marker moving irradiation points of laser beams using a galvanometer scanner and printing a desired mark composed of characters, figures and/or symbols on an object on the basis of movement loci of the irradiation points.
2. Description of the Prior Art
FIG. 8 shows a conventional laser marker of the above-described type. The shown laser marker comprises a laser oscillator 10 producing laser beams, a galvanometer scanner 11 including a pair of galvanometer mirrors 12a and 12b reflecting the laser beams produced from the laser oscillator 10, and a condensing lens 15 condensing the reflected laser beams so that the laser beams are irradiated onto an object on which a mark is to be printed. Electric motors 13a and 13b are provided for changing angles of reflection of the mirrors 12a and 12b respectively. The laser beam is scanned horizontally in FIG. 8 or in the X direction by the mirror 12a, whereas the laser beam is scanned in the Y direction generally perpendicular to the X direction by the mirror 12b. A control device 14 is provided for controlling the angles of reflection of the mirrors 12a and 12b and the laser oscillator 10 so that the same is turned on and off. The control device 14 comprises a CPU 20 as a main component thereof as shown in FIG. 9. A memory 21 and an input device 22 are connected to the CPU 20.
The memory 21 stores graphic data concerning marks which can be designated prior to start of a printing operation and data of predetermined computing expressions or formulas. The graphic data includes coordinate data concerning both end points of respective component lines of each mark. More specifically, for example, graphic data of mark xe2x80x9cAxe2x80x9d includes coordinate data of end points T1 to T5 of component lines L1, L2 and L3, as shown in FIG. 10A. Furthermore, the computing expressions include those for obtaining subdivided points and those for obtaining compensation. The computing expressions for subdivided points are provided for obtaining coordinate data of a plurality of locations obtained by subdividing the component lines of the mark on the object on the basis of coordinate data of the graphic data. For example, concerning the mark xe2x80x9cA,xe2x80x9d coordinate data of a plurality of locations (points P1, P2, P3, and so on in FIG. 10A) is obtained by subdividing the component lines L1 to L3 as shown in FIG. 10A. The computing expressions for compensation are used to compensate the distortion of the laser beam due to an aberration of the lens 15.
The character xe2x80x9cAxe2x80x9d is designated by the input device 22 when it is to be printed by the conventional laser marker. The CPU 20 of the control device 14 then carries out the following steps 1 to 4:
Step 1: The CPU 20 retrieves graphic data concerning a plurality of marks stored in the memory 21 to input the graphic data (coordinate data of end points T1 to T5) corresponding to the designated mark xe2x80x9cA.xe2x80x9d
Step 2: The CPU 20 reads out the computing expressions for subdivided points from the memory 21 to compute coordinate data of a plurality of locations subdividing the component lines L1, L2 and L3 of the mark xe2x80x9cAxe2x80x9d on the basis of the coordinate data of end points T1 to T5.
Step 3: The CPU 20 reads out the computing expressions for compensation from the memory 21 to compensate distortion in the coordinate data of a plurality of the locations on the basis of the read expressions.
Step 4: The CPU 20 delivers the compensated coordinate data to the galvanometer scanner 11 cyclically for a predetermined period and further delivers an on-off signal to the laser oscillator 10.
Upon receipt of the coordinate data, the galvanometer scanner 11 scans irradiation points of the laser light produced from the laser oscillator 10 in such a manner that locations indicated by a series of coordinate data are connected together. As a result, the irradiation points are moved in the direction of arrow in FIG. 10B so that the desired mark xe2x80x9cAxe2x80x9d is printed on the object W. Japanese Unexamined Patent Application Publication No. 11-28586 (1999) discloses a laser marker of the type described above.
In the conventional laser marker, the memory stores only the coordinate data concerning the end points of the component lines of each mark as the data of marks which can be designated. Accordingly, the coordinate data is generated during the printing operation as described above. As a result, a printing speed cannot be increased so high since the CPU 20 (control device 14) needs to ensure a time for generation of coordinate data. Provision of the control device with the CPU of high processing speed type can increase the printing speed. However, the cost for the laser marker is increased with improvement in the performance of the CPU.
Therefore, an object of the present invention is to provide a laser marker which can increase the printing speed without a large increase in the cost.
The present invention provides a laser marker scanning laser beams to print a mark on an object, the laser marker comprising a laser oscillator producing laser beams, an input device designating a mark to be printed, a galvanometer scanner successively receiving coordinate data corresponding to a predetermined location on the object, the galvanometer scanner scanning the laser beams produced from the laser oscillator toward the predetermined location on the object on the basis of the coordinate data, a memory storing sets of coordinate data of a multitude of locations on the object, the locations dividing a component line of each of marks which can be designated by the input device, and a control device successively delivering the coordinate data concerning the mark designated by the input device from the memory to the galvanometer scanner.
According to the aforesaid laser marker, the memory stores the sets of coordinate data of a multitude of the locations obtained by dividing the component line of each of the marks on the object with respect to all the marks which can be designated by the input device. Accordingly, the control device need not generate coordinate data during the printing operation and merely delivers the coordinate data from the memory to the galvanometer scanner. Thus, since the conventionally required coordinate data generating time is unnecessary, the coordinate data can be supplied to the galvanometer scanner in a shorter period. Consequently, the printing speed of the laser marker can be improved without a cost increase due to an improvement in the data processing performance of the control device.